MKMapView发布内存

问题描述

我已经按照几个SO问题提供了建议，例如，为了从内存中释放 MKMapView - 我的代码在下面

I have followed the advice available in several SO questions, like this one, in order to release MKMapView from memory - my code below

- (void)viewDidDisappear:(BOOL)animated {

    [super viewDidDisappear:animated];

    self.map.mapType = MKMapTypeHybrid;
    self.map.showsUserLocation = NO;
    self.map.delegate = nil;
    [self.map removeFromSuperview];
    self.map = nil;

    self.locationManager.delegate = nil;
}

在某种程度上，它有效但不完全。让我提供一些数据。

In part, it works, but not entirely. Let me provide some data.

以下是来自Instruments的内存分配记录。

Below is the memory allocation recording from Instruments.

两个红旗（Generations）表示状态之前我在模态视图控制器中显示 MKMapView 之后我已经解除它。 MKMapView 似乎已取消分配。例如，如果我在Instruments中过滤 MKMapView 中的统计信息堆栈，则在呈现模态视图时确实会出现该对象，并且一旦关闭它就会消失。但是，在取消了地图视图后，我仍然有30多MB的内存未被释放。

The two red flags (Generations) indicate the states before I displayed MKMapViewin a modal view controller and after I have dismissed it. MKMapView seems to get deallocated. For instance, if I filter Statistics stack in Instruments for MKMapView, the object does indeed appear when the modal view is presented, and disappears once it's closed. However, having dismissed the map view, I still have 30+ MB of memory that has not been freed up.

B代（第二个红旗）数据显示有持有此内存的大量对象（和非对象）。

Generation B (second red flag) data shows that there is a large number of objects (and non-objects) that are holding this memory.

当我查看其中一个实例的扩展详细信息时，它通常会显示一个包含私有类的堆栈跟踪，我想，与地图绘制有关

When I look at extended details of one of those instances, it usually shows a stack trace that features private classes that, I guess, are related to map drawing

有谁知道如何释放所有数据？我可以/应该清理一些缓存吗？

Does anyone know how to free up all that data? Is there some cache I could/should clean?

推荐答案

在我的应用程序中，它在选项卡的控制下使用地图视图控制器视图控制器，我在静态变量中存储对 MKMapView 的引用，并反复使用相同的地图视图，而不是在中分配新的地图视图ViewDidLoad 每次都是。我的（部分）代码：

In my app, which uses the map view controller under control of a tab view controller, I store a reference to a MKMapView in a static variable and use this same map view over and over again instead of allocating a new one in ViewDidLoad every time. My (partial) code:

@implementation PubMapViewController {
    NSMutableArray *annotations;
}
static MKMapView *_mapView = nil;

- (void)viewDidLoad {
    [super viewDidLoad];
    if (!_mapView) {
        _mapView = [[MKMapView alloc] init]; // frame set up with constraints
    } else {
        [_mapView removeAnnotations:_mapView.annotations]; // precaution
    }
    [_mapViewProxy addSubview:_mapView];
    [self addConstraints:_mapView];
    [self configureView:((PubTabBarController *)self.tabBarController).detailItem];
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    [_mapView addAnnotations:annotations];
    if (annotations.count == 1) {
        [_mapView selectAnnotation:annotations[0] animated:YES];
    }
}

- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear:animated];
    [_mapView removeAnnotations:_mapView.annotations];
}

此处， configureView：设置 self.tabBarController.detailItem 的映射，设置其委托并将映射注释存储在变量 annotations 中。

Here, configureView: sets up the map for self.tabBarController.detailItem, sets its delegate and stores the map annotations in variable annotations.

地图成为界面构建器中定义的视图的子视图（实例变量 @property（弱，非原子）IBOutlet UIView * mapViewProxy; ）。地图必须获得与 mapViewProxy 相同的大小，并且当我使用autolayout时， _mapView 的帧大小完全受控制使用 addConstraints 中设置的约束（top，bottom，left和right等于 _mapView.superview ）。

The map is made a subview to a view defined in the interface builder (instance variable @property (weak, nonatomic) IBOutlet UIView *mapViewProxy;). The map must obtain the same size as mapViewProxy, and as I use autolayout, the frame size of _mapView is controlled entirely using the constraints set up in addConstraints (top, bottom, left, and right equal to _mapView.superview).

我发现必须在 viewDidDisppear：中删除​​地图中的注释，并将其添加回 viewDidAppear 。在 viewDidDisppear：中取消设置 _mapView.delegate 可能会更加干净，并将其设置回 viewDidAppear 。

I found it compulsory to remove the annotations from the map in viewDidDisppear: and to add them back in viewDidAppear. It might be even more clean to unset _mapView.delegate in viewDidDisppear: and set it back in viewDidAppear.

BTW：静态变量 _mapView 仍然误导性地带有前导下划线因为在设置之前它是一个实例变量，通过在IB中定义 MKMapView 。

BTW: The static variable _mapView still misleadingly carries the leading underscore since it was an instance variable before set up by defining the MKMapView in IB.

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